Critical of a US decision to create a 30,000 strong army led by the YPG, Turkey's president and a senior military leader have made it clear that terror groups cannot operate along its border and that NATO must take a stand.
Turkish President Recep Tayyip Erdogan on Tuesday has called on NATO to fulfill its responsibilities towards to its partners.
"NATO, you are obliged to take a stand against those who harass the borders of one of your partners," he said.
"To date, what position have you adopted?" he asked, speaking at the governing Justice and Development (AK) Party's parliamentary group meeting in Ankara.
Erdogan's comments were echoed in Brussels by Chief of General Staff, Hulusi Akar, who on Tuesday said Ankara would not allow the PKK-related groups to be supported and armed under the guise that the terror group is an "operational partner."
"We cannot and will not allow the terrorist organisation YPG, which has been proven as an extension of the PKK, to be supported and armed under the guise of it being an operational partner," Akar said during a speech at a session of the 178th Military Committee in Chiefs of Defense Session at the NATO headquarters in Brussels.
TRT World's Andrew Hopkins has more.
The remarks from both men came following revelations earlier this week that the US-led international coalition against Daesh on Sunday would be establishing a 30,000-strong new border security force with the Syrian Democratic Forces (SDF) – the US-backed group, controlled and manned by the YPG militants in Syria.
"We expect the US to reverse the mistake as soon as possible," Akar said.
He said NATO should not "discriminate" among terrorist organisations in the fight against terrorism.
The army chief said fighting against the YPG is as "important" as fighting Daesh.
Erdogan said that the Turkish army would conduct the operations with the assistance of Syrian opposition.
"This fight is made for them. We are helping our brothers there so that they can protect their own territories," said Erdogan.
He told the parliamentary group meeting in Ankara that Turkey would "destroy" all terror spots in Syria one by one, starting with the Afrin and Manbij regions.
Erdogan recalled Turkey's successful seven-month Operation Euphrates Shield, which ended in March 2017.
"In a short span of time, we will destroy all terror nests one by one in Syria, starting from Afrin and Manbij regions," said Erdogan.
"Those who stabbed us in the back appearing like our allies cannot prevent it."
Turkey has long protested the US support for the PKK-linked PYD and YPG groups in Syria.
Ankara considers the PYD and its military wing the YPG as the Syrian offshoot of the PKK terrorist organisation while Washington sees it as a "reliable ally" in its fight against Daesh in Syria.
Listed as a terrorist organisation by Turkey, the US and the EU, the PKK has waged a terror campaign against Turkey for more than 30 years, leading to the deaths of more than 40,000 security forces and civilians.
On Saturday, Turkish security forces hit several YPG targets in Afrin to prevent a "terror corridor" from forming along Turkey's borders.
Afrin is a district of Aleppo province near the Turkish-Syria border.